Bonding, pools and hot tubs

[jes25]

OK. I am a little confused on why we bond pools and Hot tubs. For pools we are connecting the bond to eliminate voltage gradients and not to clear any faults according to FPN 680.26 and the commentary that follows in the handbook. I still am a little unclear on the whole " voltage gradient" thing but I think I roughly grasp the concept.

Now fast forward to bonding for indoor hot tubs 680.43 (D) We have no mention of voltage gradients yet similar requirements. The term "unlikely to become energized" in the exception tells me the bonding required for this section is to clear faults, but if the bonding is to clear faults what is part (F) all about?? Why hook a bond to a pump thats already has an EGC. Is the concern voltage gradients traveling through the copper water lines??[/i]

 

[George Stolz]

Saturated people are very vulnerable to voltage. With the low skin resistance, then it becomes increasingly important to ensure there are no differences in potential the saturated person could be exposed to.

Instead of guessing at what could cause the voltages (the possibilities are endless) the NEC elects to construct an effective equipotential bonding grid that most things won't overcome.

If you were to rely on the EGC of the pump to go back to the panel, then back to the service, then along the GEC to the water line, then back through the water heater, and finally back to the jetted tub's water line, would you expect them to be exactly the same voltage? It would be hard to guarantee. Connecting them together on the spot is very effective.

 

[dlhoule]

I agree George.

Not only that; but when I get saturated I sometimes find it hard to stand up let alone have any concerns about my safety. :lol:

 

[jes25]

My point is it seems 680.43 calls for bonding to clear faults and possible voltage gradients, where as 680.26 says specfically its not to clear faults.

What got me thinking is, in the event a tub has a double insulated motor would it not be benificial to make sure the bonding is connected to the pump motor EGC?

 

[george t. everett]

dlhoule,
I have the same problem.

 

[George Stolz]

My point is it seems 680.43 calls for bonding to clear faults and possible voltage gradients, where as 680.26 says specfically its not to clear faults.

As I sat here scratching my head at what prompted this, I realized you're referring to the handbook descriptions. I don't have a handbook, so I can't be of help there. But I believe that all this bonding is for equipotential purposes, with fault clearing being a side effect of everything being connected to a possible fault-clearing path.

They are both equally prone to connection to a fault-clearing path, as they both are required to bond to motors that are already required to have an EGC. So I don't understand the handbook's take on this either, it doesn't appear to hold water to exclude one or the other.

What got me thinking is, in the event a tub has a double insulated motor would it not be benificial to make sure the bonding is connected to the pump motor EGC?

It's legal, but not required, as you're aware. The double insulation is intended to replace bonding, so there would likely be no benefit to the connection you're thinking of. But it couldn't hurt anything, IMO.